Lead pencil lead



Patented May 25, 1954 LEAD PENCIL LEAD Ralph (Ralf) Valentine Maneval,Glendale, Calif., assignor to A. W. Faber-Castell Pencil Co., Inc.,Newark, N. J a corporation of New Jersey No Drawing. Application June 4,1951, Serial No. 229,867

1 Claim. 1

This invention relates to an improved composition for forming leads usedin lead pencils and it is one object of the invention to provide a leadhaving special ingredients mixed therewith which impart increasedopaqueness to the lead and thus cause lines drawn with a pencil to besharper and more clearly defined.

Another object of the invention is to provide an improved pencil leadwherein the opaqueness may be controlled by mixing predeterminedquantities of cadmium yellow or chrome to clay which is then mixed withgraphite to form the improved lead pencil lead.

Another object of the invention is to provide an improved lead pencillead formed of ingredients which are readily obtainable and are easilymixed with each other.

The ingredients used for producing the improved lead pencil lead are, asfollows:

30% Cadmium yellow or Chrome yellow, mixed with 30% clay, the mixturebeing then mixed with 40% graphite.

While the above formulae specifies proportions which have been founddesirable to produce lead pencil leads for drawing lines of maximumopaqueness or density, it will be understood that various changes in theproportions and minor details may be resorted to without departing fromthe spirit of the invention.

When the improved lead is being made and it is desired to have a maximumdegree of opaqueness, which is greater than heretofore obtainable,cadmium or chrome (red or yellow) is mixed with damp clay in theproportions set forth until they are thoroughly intermingled. After thecadmium or chrome has been thoroughly mixed with the clay, the mixtureis added to the graphite in the proportion called for and thoroughlymixed therewith. The mixture is then ready for proceeding in the usualmanner, which consists of extruding the mixture through dies underextreme pressure, cutting the extrusion into pieces of the desiredlength which are laid out to dry until they may be handled. and thenplacing the leads in a crucible and firing them with intense heat andthus forming finished leads of predetermined dimensions and hardness.

The advantage obtained by forming leads for pencils as set forth is thata pencil having the improved lead, especially a drawing pencil, willmake lines which are very opaque and produce a drawing from which clearblue prints or photographic copies may be made showing pencil lineswhich are very sharp and clear. In tests, it has been found thatdrawings made with pencils provided with the improved lead have lineswhich are, at least, 25% greater in opaqueness than drawings made withpencils now available.

Having thus described my invention, what is claimed is:

A lead pencil lead consisting of 30% cadmium yellow, 30% clay and 40%graphite.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,970,603 Grosman Aug. 21, 1934 FOREIGN PATENTS Number CountryDate 4,473 Great Britain of 1874 4,976 Great Britain of 1885 216,420Great Britain May 29, 1924 OTHER REFERENCES The National PaintDictionary, 2nd Ed., Stewart-1942, pages 29 and 34.

